TL;DR
Most temporary email services offer a free tier and a paid upgrade. Free temp email gives you the basics. You get a disposable address, a short inbox...
Aspect
Free Temporary Email
Paid/Premium Temporary Email
Inbox Duration
It takes 10 minutes to 24 hours. The inbox locks or deletes after expiry. Free isn't for recurring use. NukeMail offers 24 hours of active access on the free tier. It's the longest free window available.
Your inbox lasts for days, weeks or months based on your plan. Some premium tiers keep your inbox active as long as you pay. NukeMail premium costs $3/week, $9/month or $20/three months. You can use this paid service for ongoing tasks that require a persistent private address.
Number of Addresses
You're usually limited to one address at a time. If you want a new one, the old one is gone. This works for most one-off signups where you only need a single address.
You can manage multiple addresses under one account. NukeMail premium lets you hold up to 20 addresses at once. This is useful if you are testing several signups or need separate addresses for different purposes like keeping your shopping and social media accounts apart.
Domain Quality
Free addresses use popular temp email domains that appear on many website blocklists. The most commonly used free domains are also the ones that get blocked the most. It can be annoying when a website rejects your address during signup.
Premium tiers often include access to fresher and less-known domains that haven't been added to blocklists yet. Some services keep premium-only domains for paying users. This improves your acceptance rates on websites that check for disposable email addresses.
Advertisements
Most free temp email services show ads. Some are tasteful but others are intrusive. Ad-heavy services make reading emails difficult. This is a problem on mobile since screen space is limited and ads take up valuable real estate.
There are no ads here. The interface stays focused on the product. You'll notice the difference on mobile because there aren't any ad banners fighting for screen space. Reading your email is much better when you don't have visual clutter getting in the way.
Attachment Support
Attachments are often limited or missing entirely. Free tiers might strip attachments from incoming emails so the service saves on server costs. This can be a problem if a verification process sends a PDF or document you need to access.
You can receive attachments like PDFs, images and other files. This is important for verification processes that send documents or for services that email receipts as PDF attachments instead of inline HTML.
Data Recovery
Once the free inbox expires your data is gone. You can't recover emails you received during the active period. If you forgot to copy a verification code before the inbox expired you're out of luck.
Some paid services keep your data in a locked state after expiry so you can re-subscribe and recover it. NukeMail keeps free inbox data in a locked state for 14 days. You can upgrade to premium during that window to unlock everything. This helps if you realize days later that you needed a verification code or receipt.
Support
No customer support. You get what you get. If something doesn't work, there's nobody to ask. Free services are generally "as-is" with no service level expectations.
Some premium services provide email support or priority help. It isn't always fast but you have a channel for reporting issues. Paying customers also get more attention when domains are blocked or technical problems arise.
Verdict
Free temporary email works well for occasional one-time use. If you only need a throwaway address once a week or less, paying for temp email isn't worth the cost. The free tier handles quick verifications and one-off signups without any trouble.
Paying for temp email is worth it if you use it often, need addresses that bypass blocklists, manage multiple addresses at once or want to access emails after the free time window ends. You get an ad-free experience and better domain quality which are the most noticeable daily improvements.
Think about how often you use this. If you are reaching for temp email multiple times per week, the small cost of a premium tier will save you time and annoyance. If you only need it once a month, the free version is fine.
A big benefit of paid temp email is the data recovery window. You can go back and unlock a locked inbox days after it expires. This has saved many users who realized too late that they needed a verification code or account detail from an email they received during the free window.
If you're a heavy temp email user, you should check if an email alias service is cheaper for your needs. If you're paying $9/month for Nukemail premium and using it for signups you intend to keep for a while, a $3-4/month alias service might work better. You can still use free temp email for the truly throwaway stuff.